In this diet conscious society, the regretful and painful abstinence from sweets and high calorie foods is necessary if one wishes to be fit and trim. Ice cream and other frozen novelty desserts often ranks high on the list of no-nos and must be foresworn much to the dismay of many sweet tooths. Whereas aspartame has become a very popular dietary sweetener in low-calorie soft drinks and other beverages (Schlatter et al. U.S. Pat. No. 3,492,131), the realization of a truly satisfactory low-calorie frozen dessert has not yet, until now, been achieved.
The problem in this area is that when sugar is removed from most if not all foodstuffs in an effort to reduce the caloric content, more than just sweet taste is noticeably removed. Sugar contributes to the mouthfeel of a particular food product and provides bulk or structure. Therefore, removal of the sugar consequently removes much of sugar's bulk and thereby renders the texture or consistency of the food unsatisfactory. As a result, the mere removal and replacement of sugar with a high potency sweetener does not result in an appreciably satisfactory product since the sweetener lacks the bulk of sugar.
Understandably then, in order to produce a frozen dessert, yogurt or confection with no additional sugar added, a bulking agent must be added to the mix together with the high potency sweetener such as aspartame. The bulking agents currently available either add as many calories to the product as sucrose would were it not removed (as is in the case of the maltodextrins) and/or will have deleterious side effects such as diarrhea (as in the case of polydextrose and sorbitol).
If sugar is removed from a product, the bulking agent is required to be added in order to perform the functions (other than sweetness) of sucrose in order to obtain an acceptable product. If sugar is removed from a frozen dairy dessert in an effort to reduce calories for example, the absence of an added bulking agent will result in a dessert that is unacceptably hard and icy when frozen. Ice crystal formation from any unbound water becomes prevalent and the overall sensory perception is unpalatable. Ideally, the frozen dessert should maintain a relatively high degree of softness when serving, and should not require a large tempering time before serving to attain the desired soft state.
It is an object of the present invention to provide a method for the production of frozen dairy desserts and frozen yogurt wherein the sugar (sucrose and/or bulk contributing sweetener) has been completely removed without requiring any additional bulking agents. This is achieved through a process including the enzymatic treatment of the disaccharide sugars naturally present in milk (lactose) so as to reduce them to their monosaccharide components. More specifically, milk ingredients traditionally used in the manufacture of ice cream, ice milk and yogurt are treated with beta-galactosidase which cleaves lactose into glucose and galactose and are heated for extended periods of time to provide a superior texture. This not only results in an increase in the sweetness of the composition, but also surprisingly does not require the addition of bulking agents in order to maintain acceptable consistency, palatability and mouthfeel.
The use of an enzyme, particularly beta-galactosidase (lactase), in milk or milk based products, to reduce lactose to its constituents is well known in the art. The use of lactase to hydzolyze lactose to its monosaccharide constituents in milk and whey products, including frozen dessert applications is described by Holsinger, V., Applications of Lactose Modified Milk and Whey; Food Tech. 35 (1978). Trzecieski, U.S. Pat. No. 4,333,953 discloses the use of non-fat milk solids with lactase to produce a creamy ice milk.
U.S. Pat. No. 4,333,954, also to Trzecieski, also discloses a soft ice cream wherein lactase is added in order to reduce the ice crystallization problems of lactose in the ice cream. This is the familiar `sandy texture` that results when 20-30% of the milk solid non-fat is replaced by demineralized whey powder. The sandiness defect has been recognized to be a direct function of the amount of lactose present in the ice cream which can be removed by the hydrolysis to its monosaccharide components by lactase. Albrecht, T., et al., Sandiness Defect in Ice Cream, Ice Cream Review 22 (1956). None of the prior art however, teaches the hydrolysis of lactose, without subsequently putting in a bulking agent such as sorbitol or dextrose to replace the volume once occupied by the sugar.
EP 0 308 091 to Greenberg et al discloses the production of low and non-fat frozen desserts. The desserts are characterized by having high levels of whey protein with specific casein to whey ratios and have a low amount of lactose initially present in the dairy mix (0-10 percent by weigh;). The reference further suggests that the specifically defined mixture used to form the dessert may be heated to between about 82.degree.-85.degree. C. for between about 20 and 30 minutes when heated in a batch mode and to about 102.degree. C. for about 5 to 8 minutes when used in a continuous mode. The heating is performed to substantially denature the whey protein associated with the skim milk and the whey protein concentrate. The sweet properties of the frozen dessert are obtained by utilizing sucrose or the replacement of a portion of the sucrose with a high potency sweetening agent while maintaining approximately the same level of solids.
The existing prior art demonstrates that sugar (sucrose) or other carbohydrate sweeteners can be partially replaced in frozen desserts and confections by hydrolyzing lactose to form glucose and galactose. Addition of ingredients such as whey (high lactose) have been used as a partial replacement for sucrose; however no one has demonstrated the complete removal of sucrose and/or added carbohydrate sweeteners in a frozen dairy product which further has a desirable texture.